To actually make a menu collapsible when the browser window is under a certain width, you should use the following Bootstrap classes: .collapse and .navbar-collapse. So, wrapping your links in a div with the aforementioned classes should hide the menu.

Now you’ll have hidden the menu, but I’m almost certain you’ll want a way to show/hide the menu when you need to. Take a look at the following link which should teach you what you need and give you a better understanding of how navbars in Bootstrap work: https://getbootstrap.com/components/#navbar.